The present invention relates to an aqueous emulsion resin for producing memory foam and a method for manufacturing memory foam products, especially to a hydrophilic EVA (ethylene-vinyl acetate) memory foam made from aqueous emulsion resin with good vibration absorption, even pressure distribution and pressure relief, moisture absorption, heat absorption, low temperature resistance and non-toxicity, and a manufacturing method thereof.
Generally, polyurethane (PU) foam has been widely used in various products such as pillows, medical mattresses, office chair cushions, bed mattresses or shoe materials. Now PU memory foam with uniform pressure relief is available on the market. The PU memory foam is made from a mixture of polyether polyol (0.5˜90%), isocyanate (2˜60%) and acrylic resin (0.5˜50%). The above materials are mixed evenly at room temperature and then is added with carbon dioxide (CO2) produced by reaction of water or other foaming agents with low volatility such as methylene chloride (CH2Cl2). Next pour the mixture into a mold for various products including pillows, medical mattresses, office chair cushions, bed mattresses or shoe materials. The temperature is controlled between 30° C.˜50° C. and the foaming time is 5-10 minutes to produce molded foam. Some years ago, American company Frisby has ever used heat absorption particles (a kind of microencapsulated particle) as a filler of the foam to produce fabrics and hydrophilic (porous) foam with insulating and cooling effects. The foam is applied to various products such as home furnishing or medical beds. However, the foam and integral skin foam added with the microencapsulated particles don't have obvious temperature control effect. Sometimes there is even no difference between these foam and those without the microencapsulated particles. The PU memory foam available now has following disadvantages:
<1 > The conventional PU memory foam is hydrophobic so that it has poor moisture absorption property and heat absorption property. While in contact with users' skin, the moisture and heat generated by the users are unable to be dissipated. Thus heat is accumulated in the contact area quite fast and the users are hot and sweltering. This has negative effects on the applications of the foam.
<2 > Although the PU memory foam is soft and flexible, it doesn't have low temperature resistance. Due to high temperature sensitivity, the PU memory foam is getting rigid when the temperature is lower than 10° C. Once the ambient temperature is lower than 5° C., the PU memory foam is as hard as wood. Thus the temperature must be increased to a certain degrees and the memory foam will become flexible while being used in cold places. There is restriction on the ambient temperature and the applications of the memory foam are also affected.
<3 > The service life of the memory foam is under influence of the poor oxidation resistance and poor hydrolysis resistance.
<4 > After the reaction completed, there is still a lot of TDA (Toluene diamine) or MDA (methylene diphenyl diamine) residual in the conventional hydrophobic PU foam so that the foam is toxic while the residual amine catalyst in the molded foam causes an unpleasant order. Both affects the use of pillows, mattresses and cushions. Moreover, the conventional foam is not durable, easy to be oxidized or reacted with perfume, alcohols to become powder.
Thus there is room for improvement and a need to provide novel memory foam that meets user's requirements on quality, functions and comfort.